THIS invention relates to a radiation detector comprising diamond material and to a method of manufacturing the radiation detector.
Semiconductors can be configured to make solid-state ionisation chambers for detecting ionising radiation through the generation of electron-hole pairs within the semiconducting material. Provided the material is sufficiently free from electronic traps, the charge generated by the ionising radiation can be swept (through the application of an electric field) to suitable electrical electrodes and then measured by an appropriate external electronic circuit. Although silicon is the current material of choice for many such detectors, there are alternative materials available. Diamond is a wide band-gap semiconductor and can be configured to make a radiation detector. Diamond-based radiation detectors have been reported in the literature, for example WO2004023160. However, there is a requirement for a very robust radiation detector for environments that are hostile in the sense of the physical environment and the radiation environment, which is a requirement that has not been adequately addressed.
Solid-state ionisation chambers based upon silicon, currently used for the detection and monitoring of alpha and beta particles (or radiation) in particular, are not sufficiently robust enough for use in environments such as nuclear installations. In addition, silicon-based detectors are sensitive not only to temperature, and thus require compensation electronics, but also to light in the visible spectrum and therefore require an opaque coating on the outermost surface, which must be thin enough to still allow the alpha and beta particles to pass through. Such detectors are used in the decommissioning as well as in the day to day running of nuclear power plants and the environments are thus often dusty and erosive.
In such circumstances, the detectors are frequently damaged during the cleaning of the outermost surface, either by scratching through the thin opaque outer coating (thus rendering the detector susceptible to light) or by damaging the delicate device structure itself. As such detectors are often part of safety systems, the risk of false alarms caused by light reaching the detector element or the possibility of total failure of the device due to damage during routine cleaning are important considerations.
It is an object of the invention to provide a relatively robust and hence more reliable detector.